[SEL] Curved spokes ...engine rotation

[Steve Royster]

I'm going to go home tonight and get a big sledge hammer and "test" the 
spokes on all my engines! Thank you Rob for sharing this information for the 
safety of the SEL!  Steve Royster


>From: "Rob Skinner" <rskinner at rustyiron.com>
>Reply-To: The SEL email discussion list <sel at lists.stationary-engine.com>
>To: "'The SEL email discussion list'" <sel at lists.stationary-engine.com>
>Subject: RE: [SEL] Curved spokes ...engine rotation
>Date: Wed, 24 May 2006 08:47:25 -0700
>
>
> >If the flywheel runs the opposite way the outer
> > rim will tend to wan't to fold in on itself.
>
>Right you are, Lindsay.  Renowned engine builder Sheldon
>Brown, partner of Jeremiah Cochran, studied the issue in
>great detail.  Here is what he wrote in his Famous Flywheel
>Treatise of 1904:
>
>Are your flywheels spoked right, or are they giving you
>trouble?
>Many engineers would answer with a rueful "Right!"
>
>Spoke Cracking Leads to Flywheel Breakage!
>Thanks to superior American technology, modern engines are
>more powerful than ever. At the same time, the trend to
>lighter flywheels and fewer spokes continues.
>
>As a result of the higher stresses and cutting-edge
>construction, a fundamental design flaw in existing
>flywheels comes to light. Millions of engines are suffering
>cracked or broken spokes usually on the left side flywheel,
>leading to poor fuel economy at best, or getting left behind
>by your competition, or, in more severe cases, injury or
>death!
>
>Older flywheels were so over-built that they made up for
>incompetent design by having lots of heavy curved spokes and
>heavier-than-necessary rims. Even today, most right side
>flywheels hold up alright, because they still have more
>spokes than are needed to cope with the usual loads
>experienced by flywheels...but what about the all-important
>left flywheel?
>
>While the right side spokes tend to hold up alright, the
>left spokes are often left with insufficient strength. If a
>left spoke is cracked, there's no way that the engine can
>run right...you'll suffer catastrophic flywheel breakage due
>to metal fatigue on the left spokes.
>
>Go right now to wherever you left your engine, and check the
>spoke tension of your right wheel by plinking the spokes
>with a sledge hammer and listening to the tone. You'll
>probably find that the right side spokes are at the right
>tone, but that the left spokes will be less melodious. When
>you plunk the left spokes you'll notice that the pitch of
>the plunk is considerably lower than that of the right
>spokes. Why is this?
>
>The Myth of "Bent Spokes"
>Believe it or not, many of the unscrupulous con-artists that
>are so common in the engine industry will try to get you to
>believe that this is a "feature!" Yeah, right!
>
>They'll give you some spiel about a mystical property called
>"curve", which supposedly has something to do with the fact
>that the belt is on the right side. This is, of course,
>complete nonsense, since the belt never touches the
>flywheel, as long as your machinery is aligned just right.
>
>History Lesson Part 1.
>These idiots must have been left back in school when it was
>time to study history. Everybody knows that in the early
>days of engines, there was a problem with the left flywheels
>falling off.
>
>This was solved by the Wright brothers, when they invented
>the system of using a left-hand thread on the left flywheel
>bolt.
>
>Precession
>You might think that this would not be right, and that the
>Wright brothers had it backwards, because the friction of
>the main bearings would tend to turn the right flywheel to
>the left and the left flywheel to the right. Thus, the
>right-handed right flywheel should fall right off, while the
>left handed left flywheel would be left in place...but it
>doesn't work that way; instead an interaction with the
>Earth's magnetic field sets up eddy currents right in side
>the crankshaft, leading to a tendency for the flywheels to
>tighten themselves, as if by magic.
>
>History Lesson Part 2.
>When Nicolas Otto and Tullio Crossley independently invented
>the engine, back in the olden times, they used normal
>right-handed threading for the crankshaft main bearing caps.
>This worked alright for the left caps, but it was discovered
>that the right cap would tend to unscrew itself in use,
>unless the engine was left out in the rain, where rust could
>help to immobilize the threads.
>
>The great British engine inventor Dugald Clerk cured this
>problem by making the right crankshaft main bearing cap have
>left-hand threads, so that, even if it starts a little bit
>loose, it will tighten itself right up.
>
>The French were slow to pick up on this improved technique,
>and many German engines are still made with wrong-way
>threading, but the rest of the world has picked up on this,
>and the vast majority of engines now have main bearing caps
>that are threaded the right way: right threads on the left
>side, left threads on the right side.
>
>The Lessons of History
>Like many great inventions, bilateral obverse threading
>seems completely obvious once it has been explained; the
>solution to the problem of left flywheel breakage is, in
>fact just a simple matter of using a left-hand threading on
>the clamps that run to the left side of the flywheel!
>
>This completely eliminates the precession effect that tends
>to loosen left side flywheels in old-fashioned engines that
>use right-hand threading!
>
>Flywheel Building Issues
>Since I'm a practical mechanic as well as an inventor, I
>couldn't overlook the confusion that having two different
>types of bolts could cause. I've come up with an ingenious
>solution to the problem, however:
>
>As an optional accessory item to bilateral obverse thread
>systems, we are making available special color-coded bolts
>to help the engine builder keep track of which is which.
>Since left hand bolts look just like ordinary bolts, we
>offer special bright red bolts to fit the right-hand
>threaded spokes still used on the right side of the wheel.
>This prevents them from becoming confused with the left-hand
>threaded bolts.
>
>What About the Southern Hemisphere?
>Well, what about it? It is well known that in the Southern
>hemisphere, the problem of left flywheels loosening up does
>not occur, but rather it is the right flywheels that loosen
>up if left to their own devices.
>
>Hence, engineers who run engines mainly in the Southern
>hemisphere should use left hand threads on the right side
>flywheels, not the left.
>
>Honesty compels me to admit that for engineers who live and
>run engines within 50 miles of the Equator, any bolts will
>offer little functional value.
>
>Engineers who regularly travel back and forth between the
>Northern and Southern hemispheres would be well advised to
>swap the flywheel bolts side-to-side after crossing the
>equator.
>
>
>
>
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